Megafossil Evidence for Ordovician/Silurian Terestrial Biotas

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EAR-0308931MEGAFOSSIL EVIDENCE FOR ORDOVICIAN-SILURIAN TERRESTRIAL BIOTASGar W. Rothwell (EAR-0308931) Ohio UniversityABSTRACTThis research explores the origins of complex life on land, with an emphasis on establishment of the first terrestrial ecosystems. The work focuses on fossilized communities of organisms that inhabited the land surface at least 440 million years ago, and that provide the first direct evidence for colonization of the land. These communities are represented by abundant carbonaceous meso- and megafossils of thalloid organisms and/or symbiotic associations that are preserved in Upper Ordovician and Lower Silurian fluvial and deltaic deposits of the Appalachian Basin. Specimens are the oldest macroscopic terrestrial fossils ever discovered, demonstrating that the earliest complex land organisms had much greater fossilization potential than is currently recognized. They also document that a substantial ground cover of thalloid forms was established on the land far earlier than presently known. Goals of the proposed research are to develop fundamental knowledge about terrestrial life during the crucial but poorly known time interval between initial colonization of land by complex organisms and the emergence of vascular plants. Investigations of these Ordovician-Silurian terrestrial fossils focus on 1) documenting the first land communities, 2) determining the morphological, anatomical and ultrastructural characters of individual fossils, and 3) beginning to develop an understanding of the diversity, systematic affinities, and biological interactions of the fossilized organisms. These goals will be achieved through laboratory preparations and character determinations for fossils that already have been collected. The work is being conducted by the PI, and by graduate and undergraduate student researchers at Ohio University. Systematic investigations are being pursued through collaborations with colleagues who are experts on either the living organisms to which the fossils are most likely related, or on fossil palynomorphs from contemporaneous strata. Results will be disseminated by publications and presentations at national and international meetings, with additional educational outreach being achieved through undergraduate student laboratory exercises, and by posting of the new findings on internet data bases.